1. Field of the Invention
The present invention relates to an image processing technology for enlarging/reducing an image displayed on a display, or moving the image vertically or horizontally.
2. Description of the Related Art
Home entertainment systems are proposed in which not only a game program can be run but also moving images can be played back. In this home entertainment system, a graphic processing unit (GPU) generates three-dimensional images in which polygons are used.    [patent document No. 1] U.S. Pat. No. 6,563,999
In the related art, there is proposed a technology for enlarging/reducing a display image or moving the image vertically or horizontally using tile images at a plurality of resolutions generated from digital images such as high-definition photographs. According to such an image processing technology, images at a plurality of resolutions are generated by reducing an original image in size in a plurality of stages, dividing the image in each layer into one or a plurality of tile images, so as to represent the original image using a hierarchical structure. Normally, the image at the lowest resolution comprises a single tile image. The original image, which has the highest resolution, comprises the largest number of tile images. The image processing device is adapted to enlarge or reduce a display image efficiently by switching a tile image currently used to a tile image in a different layer.
In such an image processing device, the display image may not be smoothly enlarged or reduced at the time of switching the tile image. A similar situation may occur when the display image is moved vertically or horizontally, i.e. the display image may not be moved smoothly when tile image located in the direction of movement is switched into use. When display images are not modified continuously, the user may feel uncomfortable.